硅酸盐学报

磁控溅射法制备BaTiO₃薄膜及其结构与光学性能

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刘次捷 ¹^,²^,³ , 王思旭 ¹ , 李为 ¹ , 马云鹏 ¹ , 陈昌富 ¹ , 于涵 ¹ , 张洪雷 ²^,³ , 邓晨光 ¹ , 李千 ¹

硅酸盐学报 | 面向新一代信息技术应用的铁电薄膜与器件专题—研究论文 2025,53(9): 2479-2488

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硅酸盐学报 |面向新一代信息技术应用的铁电薄膜与器件专题—研究论文 2025 , 53 (9) : 2479 -2488

磁控溅射法制备BaTiO₃薄膜及其结构与光学性能

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刘次捷¹^,²^,³, 王思旭¹, 李为¹, 马云鹏¹, 陈昌富¹, 于涵¹, 张洪雷²^,³, 邓晨光¹, 李千¹

作者信息

^1．清华大学材料学院，北京 100084

^2．诺丁汉大学卓越灯塔计划（宁波）创新研究院，浙江宁波 315020

^3．宁波诺丁汉大学理工学院，浙江宁波 315100

通讯作者:

李千（1986—），男，博士，副教授。

作者简介:

刘次捷（2000—），女，博士研究生。

Investigation of Structural and Optical Properties in BaTiO₃ Thin Films Prepared by Radio Frequency Magnetron Sputtering

Cijie LIU¹^,²^,³, Sixu WANG¹, Wei LI¹, YunPeng MA¹, Changfu CHEN¹, Han YU¹, Honglei ZHANG²^,³, Chenguang DENG¹, Qian LI¹

Affiliations

^1.School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China

^2.Nottingham Ningbo China Beacons of Excellence Research and Innovation Institute. Ningbo 315020, Zhejiang, China

^3.Faculty of Science and Engineering, University of Nottingham Ningbo China. Ningbo 315100, Zhejiang, China

Corresponding Author:

LI Qian (1986-), male, Ph.D., Associate Professor. E-mail: qianli_mse@tsinghua.edu.cn

LIU Cijie (2000-), female, Doctoral Candidate. E-mail: shxcl4@nottingham.edu.cn

出版时间: 2025-09-20 doi: 10.14062/j.issn.0454-5648.20250316

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摘要

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BaTiO₃（BTO）薄膜因其优异的压电性、铁电性和非线性光学性能，在电光功能材料领域具有广泛的应用前景。本工作采用射频磁控溅射法，在（001）（La, Sr）（Al, Ta）O₃（LSAT）与（110）GdScO₃（GSO）单晶衬底上成功外延沉积了BTO薄膜，研究了衬底温度、靶材与基板之间的距离（靶基距）、O₂与Ar的体积比、射频功率及溅射时间等参数对薄膜结晶取向、生长速率及表面形貌的影响规律。结果表明，衬底温度是影响BTO薄膜结晶取向的关键因素：当沉积温度低于500 ℃时，薄膜呈非晶态，需经后续退火处理形成a-轴取向；而当沉积温度高于600 ℃时，可直接获得具有c-轴取向的结晶薄膜。进一步通过二次谐波产生（SHG）测试验证了薄膜的相结构与极化畴结构。研究明确了BTO薄膜的最佳沉积工艺条件，为其在铁电器件、压电传感器及集成光电子系统等领域的应用提供了重要技术支撑。

关键词

钛酸钡薄膜 / 射频磁控溅射 / 薄膜材料 / 二次谐波产生

Abstract

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Introduction

Ferroelectric thin films have drawn growing interest for their potential in electro-optic modulation, nonlinear optics, and integrated photonics, owing to their intrinsic spontaneous polarization. Among them, BaTiO₃ (BTO) stands out for its strong ferroelectricity, piezoelectricity, and nonlinear optical properties, making it a promising material for high-performance optoelectronic devices. To realize these functionalities, it is essential to achieve high crystallinity and controlled orientation in BTO films—especially along the c-axis, which is critical for polarization-related responses. While techniques such as pulsed laser deposition (PLD) and atomic layer deposition (ALD) have been used for BTO growth, they face challenges in scalability and substrate compatibility. Radio frequency (RF) magnetron sputtering offers a scalable alternative with good control over film uniformity and composition. However, obtaining high-quality epitaxial BTO films via sputtering remains challenging due to the sensitivity of the process to parameters like substrate temperature, gas composition, and RF power. This work systematically investigates the effects of key sputtering parameters on the structural and optical properties of c-axis-oriented BTO thin films. The relationship between deposition conditions, domain structure, and optical performance is further explored using second harmonic generation (SHG), aiming to guide the fabrication of high-quality ferroelectric films for integrated photonic applications.

Methods

Epitaxial BaTiO₃ (BTO) thin films were deposited on (001) (La,Sr)(Al,Ta)O₃ (LSAT) and (110) GdScO₃(GSO)single-crystal substrates using RF magnetron sputtering with a 2 in ceramic BTO target. The chamber pressure was maintained at 1.5 Pa, with either pure Ar or Ar/O₂ gas mixtures as the sputtering atmosphere. Substrate temperatures ranged from 25 ℃ to 750 ℃, and RF power was set at 50 W or 75 W (2.47 W/cm² and 3.70 W/cm², respectively). A 10 min pre-sputtering step was performed before each run to stabilize film composition. Structural characterization was conducted using an X-ray diffractometer (SmartLab, Rigaku) with a Cu-Kα₁ source and Ge (220) monochromator. Measurements included θ-2θ scans, rocking curves, X-ray reflectivity (XRR), and reciprocal space mapping (RSM). Surface morphology and roughness were analyzed via atomic force microscopy (AFM, tapping mode), while domain structures were evaluated using second harmonic generation (SHG) with a Ti:sapphire femtosecond laser (800 nm, 35 fs). SHG measurements were performed in reflection geometry at a 45° incidence angle. Film composition was assessed using a Zeiss GeminiSEM 500 with a windowless EDS detector at 20 kV to determine the Ba/Ti ratio. Optical constants, including refractive index (n₀) and extinction coefficient (k₀), were measured by spectroscopic ellipsometry (UVISEL plus, Horiba) and fitted using the Lorentz model. Ellipsometric thickness values were validated by XRR.

Results and discussion

The deposition temperature plays a critical role in determining the crystallinity, strain state, morphology, and polarization of BaTiO₃ (BTO) thin films grown on LSAT and GSO substrates. High-resolution X-ray diffraction (HRXRD) results show enhanced c-axis orientation and crystallinity with increasing temperature, peaking at 700 ℃ on LSAT. A further rise to 750 ℃ slightly reduces quality, likely due to defect formation. On GSO, improved Laue oscillations and narrower FWHM at 750 ℃ indicate better lattice matching and epitaxial growth. Scherrer-based estimates reveal that vertical coherence length peaks at 700 ℃ (about 32 nm) on LSAT and increases steadily on GSO, reaching about 60 nm at 750 ℃. This contrast reflects superior lattice compatibility between GSO and BTO. Reciprocal space mapping shows strain evolution with temperature. At 500 ℃, films exhibit strong in-plane tensile strain (c/a ratio < 1), which relaxes at higher temperatures as c/a exceeds 1. Calculated strain confirms this, with in-plane strain decreasing and out-of-plane strain increasing from 500 ℃ to 750 ℃. SHG measurements reveal that low-temperature films (500 ℃) favor in-plane polarization, while higher temperatures induce out-of-plane domains and complex multi-domain structures, indicating temperature-driven polarization reorientation. AFM results show the smoothest surface at 600 ℃ (RMS is 1.175 nm), with roughness slightly increasing at higher temperatures due to strain relaxation and defect formation. These findings align with XRD and XRR trends. Ellipsometry and XRR confirm that film thickness decreases from about 80 nm at 500 ℃ to about 50 nm at 600-650 ℃ due to enhanced lateral growth, then slightly increases at higher temperatures. Clearer XRR fringes at 700 ℃ indicate improved interface quality. Deposition optimization identified the best conditions as 30° angle, pure Ar atmosphere, 13.361 cm target-substrate distance, and 75 W RF power, achieving uniform and high-quality films. Finally, SEM and EDS analyses show denser, smoother films at elevated temperatures. However, Ba/Ti ratios deviated from stoichiometry (0.66-0.97), likely due to off-axis sputtering effects, contributing to strain and preferential c-axis domain formation.

Conclusions

Epitaxial BaTiO₃ (BTO) thin films were successfully deposited on (001)-oriented LSAT and (110)-oriented GSO substrates via radio-frequency (RF) magnetron sputtering. The structural, morphological, compositional, and optical properties of the films were systematically investigated. X-ray diffraction (XRD) analysis confirmed that the films predominantly crystallized in the tetragonal phase with a strong (001) preferred orientation, indicating high-quality epitaxial growth. Particularly, the film deposited on the GSO substrate at 750 ℃ exhibited superior crystallinity, as evidenced by the appearance of distinct Laue oscillations. Deposition parameters such as target-to-substrate distance, deposition angle, O₂/Ar gas volume flow ratio, and RF power were found to significantly influence the film's structure and performance. Optimal results were achieved using a target-to-substrate distance of 13.361 cm, a deposition angle of 30°, and an RF power of 75 W, with pure Ar atmosphere yielding the best film quality and highest deposition rate. The synergistic optimization of these parameters is essential for obtaining high-crystalline-quality BTO thin films and provides a solid foundation for their application in optoelectronic and ferroelectric devices.

Key words

barium titanate films / radio frequency-magnetron sputtering / film material / second harmonic generation

引用本文

刘次捷, 王思旭, 李为, 马云鹏, 陈昌富, 于涵, 张洪雷, 邓晨光, 李千. 磁控溅射法制备BaTiO₃薄膜及其结构与光学性能. 硅酸盐学报, 2025 , 53 (9) : 2479 -2488 . DOI: 10.14062/j.issn.0454-5648.20250316

Cijie LIU, Sixu WANG, Wei LI, YunPeng MA, Changfu CHEN, Han YU, Honglei ZHANG, Chenguang DENG, Qian LI. Investigation of Structural and Optical Properties in BaTiO₃ Thin Films Prepared by Radio Frequency Magnetron Sputtering[J]. Journal of the Chinese Ceramic Society, 2025 , 53 (9) : 2479 -2488 . DOI: 10.14062/j.issn.0454-5648.20250316

基金

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国家自然科学基金项目(12474087)
北京市自然科学基金(JQ24011; Z240008)

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2025年第53卷第9期

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文章信息

doi: 10.14062/j.issn.0454-5648.20250316

接收时间：2025-04-18
首发时间：2026-10-21
出版时间：2025-09-20

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出版历史

收稿日期：2025-04-18
修回日期：2025-05-16

基金

国家自然科学基金项目(12474087)

北京市自然科学基金(JQ24011; Z240008)

作者信息

^1．清华大学材料学院，北京 100084

^2．诺丁汉大学卓越灯塔计划（宁波）创新研究院，浙江宁波 315020

^3．宁波诺丁汉大学理工学院，浙江宁波 315100

通讯作者:

李千（1986—），男，博士，副教授。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20250316

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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